以下是我用汇编编写的一段代码，使用的是MDK5.15，下载到LPC824M201（Cortex-M0+内核），调用子程序的时候不能正常返回。请问问题在哪里？
源代码如下：
area reset, code, readonly preserve8 SYSCON_BASE equ 0x40048000 SYSCON_SYSAHBCLKCTRL equ (SYSCON_BASE + 0X80 MSP_TOP equ 0x10001808 export __Vectors export __Vectors_End __Vectors dcd MSP_TOP dcd Reset_Handler space 200 __Vectors_End __Vectors_Size equ __Vectors_End - __Vectors entry Reset_Handler proc export Reset_Handler movs r0, #1 movs r1, #2 movs r2, #3 movs r3, #4 bl system_init loop nop nop b loop endp system_init proc push {lr} ldr r0, =SYSCON_SYSAHBCLKCTRL ldr r1, =(1 << 7) ldr r2, =(1<< 18) orrs r1, r1, r2 str r1, [r0] pop {pc}
I can not say what exactly is wrong, but experimenting might help solve the problem.
First try this:
system_init proc ldr r0, =SYSCON_SYSAHBCLKCTRL ldr r1, =(1 << 7) ldr r2, =(1<< 18) orrs r1, r1, r2 str r1, [r0] bx lr endp
If the above works, then your stack pointer's value is probably wrong.
However, if the above does not work, try this:
system_init proc push {lr} movs r0,#17 pop {pc} endp
If this works, then there is a problem (HardFault) with the peripheral address being accessed.
If none of the above are executed, then the problem is elsewhere. Unfortunately I am not familiar with the tools you are using, so there might be some assembler-directives that are necessary.
(on the GNU assembler, it's necessary to have .thumb_func preceding all the function entry labels, plus .type Reset_Handler,%function before the reset handler, but I do not know if there are any equivalent directives on the assembler from ARM).